linux-kernel - Re: [PATCH UPDATED 1/3] vhost: replace vhost

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Date:	Sun, 25 Jul 2010 13:04:33 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Oleg Nesterov <oleg@...hat.com>,
	Sridhar Samudrala <sri@...ibm.com>,
	netdev <netdev@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dmitri Vorobiev <dmitri.vorobiev@...ial.com>,
	Jiri Kosina <jkosina@...e.cz>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH UPDATED 1/3] vhost: replace vhost_workqueue with
 per-vhost kthread

On Sun, Jul 25, 2010 at 09:41:22AM +0200, Tejun Heo wrote:
> Hello,
> 
> On 07/24/2010 09:14 PM, Michael S. Tsirkin wrote:
> >> I've created kthread_worker in wq#for-next tree and already converted
> >> ivtv to use it.  Once this lands in mainline, I think converting vhost
> >> to use it would be better choice.  kthread worker code uses basically
> >> the same logic used in the vhost_workqueue code but is better
> >> organized and documented.  So, I think it would be better to stick
> >> with the original implementation, as otherwise we're likely to just
> >> decrease test coverage without much gain.
> >>
> >>   http://git.kernel.org/?p=linux/kernel/git/tj/wq.git;a=commitdiff;h=b56c0d8937e665a27d90517ee7a746d0aa05af46;hp=53c5f5ba42c194cb13dd3083ed425f2c5b1ec439
> > 
> > Sure, if we keep using workqueue. But I'd like to investigate this
> > direction a bit more because there's discussion to switching from kthread to
> > regular threads altogether.
> 
> Hmmm? It doesn't have much to do with workqueue.  kthread_worker is a
> simple wrapper around kthread.  It now assumes kthread but changing it
> to be useable with any thread shouldn't be too hard.  Wouldn't that be
> better?

Yes, of course, when common code becomes available we should
switch to that.

> >> I don't think doing this before executing the function is correct,
> > 
> > Well, before I execute the function work is NULL, so this is skipped.
> > Correct?
> >
> >> so
> >> you'll have to release the lock, execute the function, regrab the lock
> >> and then do the flush processing.
> >>
> >> Thanks.
> > 
> > It's done in the loop, so I thought we can reuse the locking
> > done for the sake of processing the next work item.
> > Makes sense?
> 
> Yeap, right.  I think it would make much more sense to use common code
> when it becomes available but if you think the posted change is
> necessary till then, please feel free to go ahead.
> 
> Thanks.
> 
> -- 
> tejun
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